[Task] Move Out All Non-Maintained Frontend Frameworks

[gagdiez]

Description

Our frontend section explains 3 things:

1. How to add near-api-js and wallet-selector to an existing JS App
2. How to use BOS to create and publish components
3. How to use Chain hosted UI to publish and use a website

Sadly enough, both BOS and Chain Hosted UI are no longer being maintained, and it does not look like anyone is going to be maintaining them in the short term

Having frameworks that are no longer maintained creates a bad user experience, since people invest time on trying it, only to discover that it is no longer working and nobody will ever fix it

---

Acceptance Criteria

Tasks

Preview Give feedback

1. Remove relevant docs sections
2. Create a github page docs site for BOS, and move all docs there
3. Create a github page docs site for Chain UI, and move all docs there
4. Create an index page with relevant frontend gr

[flmel]

closed by #2416
deprecated docs repo can be found here:
https://deprecated-near.github.io/legacy-docs/